CVE-2026-63252 in Milo
Summary
by MITRE • 08/04/2026
In Eclipse Milo versions 0.6.0 through 1.1.4, UASC server transport handlers fail to release retained partial message chunks when a channel disconnects, allowing a remote unauthenticated client to exhaust pooled direct memory by repeatedly sending incomplete chunks and disconnecting, potentially terminating the server.
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Analysis
by VulDB Data Team • 08/04/2026
The vulnerability in Eclipse Milo versions 0.6.0 through 1.1.4 represents a critical memory management flaw within the UASC (Unified Automation Secure Channel) server transport handler implementation that directly impacts the server's ability to handle concurrent connections and maintain operational stability. This issue manifests when remote unauthenticated clients exploit a memory leak pattern by sending partial message chunks and immediately disconnecting from the channel without proper termination sequences, creating a persistent accumulation of retained memory segments within the server's direct memory pool. The flaw specifically affects the server's transport layer handling mechanism where incomplete message fragments are stored in memory buffers for potential reassembly but fail to be properly released when the underlying network channel terminates unexpectedly.
The technical exploitation of this vulnerability follows a predictable pattern that leverages the server's failure to implement proper cleanup routines during abnormal disconnection scenarios. When a client establishes a connection and begins transmitting partial chunks of data before abruptly disconnecting, the server maintains references to these partially received message segments in its pooled direct memory allocation system. This memory retention occurs because the UASC server transport handlers do not properly execute garbage collection procedures or memory deallocation routines when channel closure events occur without proper message completion. The vulnerability operates at the network transport layer where the server's memory management system fails to distinguish between legitimate partial message states and abandoned chunks that should be immediately released, creating a memory leak condition that progressively consumes available direct memory resources.
The operational impact of this vulnerability extends beyond simple resource exhaustion to potentially compromise the entire server infrastructure by causing denial of service conditions through memory starvation. As attackers repeatedly exploit this flaw, they can systematically deplete the server's direct memory pool until the application encounters out-of-memory errors and terminates operations entirely. The vulnerability affects unauthenticated clients specifically, meaning that any remote attacker with network access can initiate this attack without requiring valid credentials or authentication, making it particularly dangerous in publicly accessible server environments. This memory exhaustion scenario can lead to complete service termination where the server becomes unresponsive to legitimate client requests and may require manual restart to restore normal operations.
From a cybersecurity perspective, this vulnerability maps directly to CWE-404, which describes improper resource cleanup or release, and specifically aligns with ATT&CK technique T1499.004 for network denial of service attacks that target memory resources. The flaw represents a classic case of resource exhaustion attack where the attacker leverages legitimate server functionality to consume system resources through repeated malicious actions rather than exploiting direct code execution vulnerabilities. Organizations using affected Eclipse Milo versions should implement immediate mitigations including updating to patched releases that properly handle channel disconnection events and implement memory monitoring systems to detect unusual direct memory consumption patterns. The vulnerability also highlights the importance of proper memory management practices in high-performance server applications where resource cleanup must occur regardless of connection termination circumstances, as outlined in industry best practices for secure software development lifecycle implementations.